Grading of alkaline-earth carbonates



Patented June 9, 1925.

WALTER WILLIAM snowman, or Eas'r SHEEN, ENGLAND.

GRADING F ALKALINE-EARTH cAnBoNA'rEs.

No Drawing.

To all whom it may concern;

Be it known that I, WALTER WILLIAM PLOWMAN, a subject of the King of England, residing in East Sheen, in the county of Surrey, England, have invented certain I have found, however, that by the ac tion of an appropriate reagent upon such a carbonate in a state of (sub-division, the latter may be finely distributed throughout the liquid in which it is treated, and that under these conditions coarser material falls out andmay be separated, while the alkaline-earth carbonate recovered from its liquid dispersion, hereinafter referred to-as the suspension, is obtained in a finely-divided form. The treatment of alkalineearth carbonates in this Way therefore provides a means of obtaining them in a fine stateof division, and the word grading as used herein in this specification and claims is intended to comprise treatment of so these carbonates for this purpose itself, as

well as for the purpose of removing associated material which does not pass into suspension when treated with' thereagent i question. According to this invention, a process for grading as defined of alkaline-earth carbonates comprises forming a suspension of the carbonate by admixture of the subdivided material to be graded with a dilute 40 solution of an alkaline silicate, such as sodiumor potassium-silicate. 1* The proportion of alkaline silicate may be of the order of about 0.5 to 1.5.per cent, relatively to the weight of carbonate in the form of a 5 to 10. per cent fluid admixture of the latter. The alkaline-earth carbonate may be recovered from its suspension in any suitable way, for instance, by addition to the suspension of a suitable fiocculating reagent,

for example, a solution of alum or of gelatine, such as a solution of glue, according to the circumstances of the case such as the particular carbonate to be precipitated. In certain cases it may be advantageous a supernatant suspension.

Application filed April 14, 1922. Serial No. 552,815.

to add the flocculating reagent so gradually, or in such total quantity relatively to the quantity of alkaline silicate employed for effecting the original suspension, that the sedimentation of the flocculated carbonate is retarded, in order to allow for separation from the latter of material not previously thrown out during the period of suspension.

The suspended carbonate may also be recovered, after separation, if necessary, from any deposited material, by evaporation of the suspension to dryness.

The following examples will serve to indicate how the invention may be carried into effect, it being understood that these examples are given for illustrative purposes and not by way of limitation r. E sample I A mixture of 120 lbs. of common whiting and 1554 lbs. of soft water, equivalent to a 7.5 per cent mixture, was run into a tank, and 1 lb. of sodium silicate in aqueous solution was added and the contents of the tank well mixed, and then left to stand for about 1 hour. At the end of that time there was a separation of the mixture into two regions, an under layer of solid material, and The latter was drawn off into a second tank and was treated With 1 lb. of aluminium sulphate in the form of an aqueous solution, and the contents of the tank were then left to stand for about twenty-four to thirty-six hours. Thesupernatant liquor was then run off leaving a residue of very finely-divided alkalineearth carbonate. From the first tank in which the treatment with silicate was efl'ect ed about 48 pounds of de sit were recovered, the nature of which mdicated its suitability for the preparation of abrasive compositions.

Example I.

The same quantity of Gilders whiting was treated under similar con itions except that the reagent was pot v ium silicate. The carbonate was flocculated by addition to its suspension of a solution of glue (l -lb. of glue dimolved with 34 lbs. of waten by weight). in the case of the first example, there was obtained a very finely divided product, while about .38 lbs. of deposit remained in the fir t tank.

A sample of precipitated chalk yielded a similar product, about per cent of deposit remaining in the first tank.

'f male 111.

Example IV.

To 200 lbs'. of pulverized.strontium car- 20 bonate admixed with 2000 lbs. of soft water was added 1 lb. of potassium silicate in aqueous solution, and the mixture was left tostand for about one, hour. On addition to the suspension of'an aqueous solution of 1 lb. of commercial alum and standing for several hours, the strontiumicarbonate was precipitated in the form of a very finelydivided product.- I

According to the degree of hardness of the water with which the alkaline-earth carbona-te is mixed, it may be found necessary appropriatel to adjust the proportion rela tively to the latter of the alkaline silicate used for preparing the suspension.

Magnesium carbonate is included in the term alkaline-earth carbonate for the purpose of this invention. 1'

I claim 1 1. In the process of grading as hereinbefore defined of alkaline-earth carbonates, the steps consisting of admixing the carbonate in a state of subdivision with water in presence of an alkaline silicate in quantity suficient to effect deflocculation of the carbonate, separating the, alkaline-earth car-,.

bonate suspension so roducedfrom any ondeflocculated materia, and s parating the carbonate from its suspension.

2. In the process ofgrading as hereinbefore defined of alkaline-earth carbonates, the

. in a state of subdivision with 'water in presence of an alkaline silicate in quantity sufficient to effect deflocculation of the carbonate, separating the alkaline-earth carbonate suspension so produced from any undefiociculated material, and separatin bonate from its suspension by occulation.

3. In the process, of-grading as hereinbefore defined of alkaline-earth carbonates, the steps consisting of admixing the earbonate in a state ofsubdivision with water in resence of an alkaline silicate in quantity su cient to eifect deflocculation ofthe carbonate, allowing the mixture so produced ate from its suspension.

the can-N mixture,

flocculated material, separating the alkaline-earth carbonate suspension from the deposit, and recovering the carbonate from its suspension.

4. In the process of grading as herein before defined of alkaline-earth carbonates, the steps consisting offadmixing the carbonate with a dilute aqueous solution of an alkaline silicate containing substantially 0.50 to 1.50 per cent of the silicate relatively to the weight of the carbonate to be treated, separating the alkaline-earth carbonate suspension so produced from any undeflocculated material, and recovering the carbon- 7 5. In the process of before defined of calcium carbonate,- the steps consisting of admixing the carbonate in a state of subdivision with water in presence of'an alkaline silicate in quantity sufficient to efli'ect the deflocculation ofthecarbonate, separating the .calciunfcarbonate suspension so produced from any undeflocculated material, and recovering the 'carbonate from its suspension.

6'. In the process of grading as hereinbe- .fore defined of calcium carbonate, the steps consisting of admixing the carbonate in a state of subdivision with water in presence of sodium silicate in quantity suffi'cient to efi'ect-deflocculation of the carbonate, sep-. arating the calcium carbonate suspenslon so produced from any undeflocculated material, and recovering the carbonatefrom its suspension. 7 V

7. In the process of grading. as hereinbefore defined of calcium carbonate, the. steps consisting of admixingthe subdivided ca'rgrading as herein-- bonate with a dilute aqueous solution of T sodium silicate containing substantially 0.50 to 1.50 per cent of the silicate relatively'to the weight of calcium carbonate, separating the calcium carbonate suspension so produced from any undeflocculated material, and recovering the carbonate fromits sus pension.

'8. In the process of grading as hereinbefore defined of calcium carbonate, the steps bonate with water so as to provide a substantially '5 to 10 per cent mixture, admixing therewith a solution of alkaline silicate in quantity sufiicient to give substantially consisting of admixing the subdivided carsteps consisting of admixing the carbonate 0.50 to 1.50 per cent of silicate relatively to 1 V the weight of the carbonate in the aqueous separating the carbonate suspension so produced from any undeflocculated its suspension. e-

9., In the process of grading as hereinbefore defined of calcium carbonate, the steps consisting of admixing the subdivided carbonate with water so as to provide substantially-a 5 to 10 per cent-mixture. ad-

.material, and recovering thecarbonate from mixing therewith a solution of sodium silicate in quantity suflicient to eifect deflocculation of the calcium carbonate, separating the carbonate suspension so produced from any undeflocculated material, and re- Covering the carbonate from its suspension.

10. In the process of grading as hereinbefore defined of calcium carbonate, the steps consisting of admixing the subdivided carbonate with water so as to provide a substantially 5 to 10 per cent mixture, admixing therewith a solution of sodium silicatein quantity suflicient to give substantially 0.50

to 1.50 per cent of the sodium silicate relatively to the weight of carbonate in the aqueous mixture, separating the calcium carbonate suspension so produced from any undefioc culated material, and recovering the carbonate from itssuspension.

In testimony whereof I have signed my name to this specification in the presence of two subscribin witnesses.

WALTEI? WVILLIAM PLOWMAN.

Witnesses:

HARRY S. SLEDGE, FRANK Moons. 

